The present invention relates to material handling systems and technology, and, more particularly, to a pallet stop for use in a pallet load transport system for moving pallet loads from a pick-up location to a deposit location.
In one common application of such a pallet load transport system, a pallet load is picked up from a mainline conveyor and deposited at an automatic storage and retrieval (ASRS) crane interface station. Alternatively, a pallet load may be picked up at the crane interface station and deposited onto the mainline conveyor. In any event, the pallet load system includes a shuttle car that moves between the mainline conveyor and the crane interface station to transport the pallet load.
In pallet load transport systems of the prior art, there is a pick-up and delivery (P&D) shuttle car that transports a pallet load between a mainline conveyor and a crane interface station. Specifically, the shuttle car is supported by and moves along a track between the mainline conveyor and the crane interface station. The shuttle car itself is generally comprised of a lower carriage and an upper carriage (or lift assembly), and the upper carriage can be raised or lowered relative to the lower carriage. Accordingly, as the shuttle car carries a pallet load between the mainline conveyor and the crane interface station, the upper carriage is commonly in a raised position relative to the lower carriage, but as the shuttle car approaches the mainline conveyor or the crane interface station, it is in a lowered position to pick-up or deposit a pallet load.
Furthermore, such prior art systems often include a spring-actuated pallet stop that is forced downward against the spring force as the pallet load moved over an upper surface of the stop. Once the pallet load clears the stop, the spring force causes the stop to raise and prevent the pallet load from moving back over the stop. However, because of the nature of the spring force, the upward force on the pallet load increases as it moved over the stop and the spring is further extended. Such increased upward force could actually cause the pallet load to be forced upward and off of the shuttle car, especially if the pallet load was unusually light. Additionally, because of the constant sliding motion of the pallet load over such a spring-loaded stop, wear can prove to be a problem, and the stop often gradually shifts position, making it less effective in ensuring proper positioning of a pallet load. Thus, there remains a need for an effective and reliable pallet stop for use with pallet load transport systems.